Relative contribution of upper and lower atmosphere to integrated refractive-index profiles

We measure the wavefront coherence and the irradiance fluctuations of stellar sources to obtain integrated refractive-turbulence profiles of two regions of the atmosphere. Comparison of experimental data during our measurement program shows an equal contribution of upper and lower layers to the limitation of the optical seeing. We also note the great variability of turbulence located above 3 km up to the stratosphere, from night to night. When simultaneously operated, these two methods are suitable for astronomical site testing.